This subject matter disclosed herein relates generally to imaging systems, and more particularly, to a method and apparatus for generating images having reduced noise-related imaging artifacts.
Non-invasive imaging broadly encompasses techniques for generating images of the internal structures or regions of a person or object that are otherwise inaccessible for visual inspection. One such imaging technique is known as x-ray computed tomography (CT). CT imaging systems measure the attenuation of x-ray beams that pass through the object from numerous angles (often referred to as projection data). Based upon these measurements, a computer is able to process and reconstruct images of the portions of the object responsible for the radiation attenuation. CT imaging techniques, however, may present certain challenges when imaging dynamic internal organs, such as the heart. For example, in cardiac imaging, the motion of the heart causes inconsistencies in the projection data which, after reconstruction, may result in various artifacts such as blurring, streaking, or discontinuities. In particular, artifacts may occur during cardiac imaging when projections that are not acquired at the same point in the heart cycle, e.g., the same phase, are used to reconstruct the image.
For example, in CT reconstruction, the image function to be reconstructed is generally assumed to be stationary during the acquisition. However, the image function is a function of time as well. Therefore, motion-related artifacts may occur in the reconstructed images. In general, to reduce motion related artifacts, the image data is acquired as quickly as possible to minimize the time over which the projections which contribute to the image are acquired. However, reducing the amount of time utilized to acquire the image data results in fewer projections being acquired and thus few photons contributing to the image reconstruction. Accordingly, information from fewer total photons is available to reconstruct the final image. As a result, the final image may have increased noise because fewer projections are utilized to reconstruct the final image.